It has been proposed in U.S. Pat. No. 5,866,282 (Bourdelais et al.) to utilize a composite support material with laminated biaxially oriented polyolefin sheets as a photographic imaging material. In U.S. Pat. No. 5,866,282, biaxially oriented polyolefin sheets are extrusion laminated to cellulose paper to create a support for silver halide imaging layers. The biaxially oriented sheets described in U.S. Pat. No. 5,866,282 have a microvoided layer in combination with coextruded layers that contain white pigments such as TiO.sub.2 above and below the microvoided layer. The composite imaging support structure described in U.S. Pat. No. 5,866,282 has been found to be more durable, sharper and brighter than prior art photographic paper imaging supports that use cast melt extruded polyethylene layers coated on cellulose paper.
A photographic element with a microvoided sheet of opalescence is described in U.S. Pat. No. 5,888,681 (Gula et al.). In U.S. Pat. No. 5,888,681 microvoided polymer sheets with microvoided polymer layer located between a cellulose paper base and developed silver halide imaging provide an image with a opalescence appearance. While the opalescence appearance is present in the image, the image suffers from a loss of image sharpness or acutance, a higher density minimum position and a decrease in printing speed compared to typical a photographic image on a white, reflecting base. It would be desirable if the desirable opalescent look of the image could be maintained while improving printing speed, increasing sharpness and decreasing density minimum.
Prior art reflective photographic display materials with a polyester base use a TiO.sub.2 pigmented polyester base onto which light sensitive silver halide emulsions are coated. It has been proposed in WO 94/04961 to use opaque polyester containing 10% to 25% TiO.sub.2 for a photographic support. The TiO.sub.2 in the polyester or paper base is always located directly under the image layer to provide optimum sharpness and reflectivity. The TiO.sub.2 also gives the base support a slight yellow tint which is undesirable for a photographic material. Furthermore the TiO.sub.2 or other pigments corrupts the purity of the dye color. This is particularly true for reflective photographic images. For use as a photographic material, the polyester or other substrate support containing TiO.sub.2 must be tinted blue to offset the yellow tint of the gelatin binder causing a loss in desirable whiteness and adding cost to the display material. Prior art photographic translucent display materials with incorporated diffusers which include transmission and reflective display materials typically contain some level of white pigment to either diffuse the backlighting source in the case of transmission display materials or provide the desired reflective properties in the case of a reflective display material.
In addition to the use of white pigments in reflective consumer photographs, white pigments are also utilized in photographic display materials for diffusion of illumination light source. While the use of white pigments in display materials does provide the desired diffusion and reflection properties, the white pigments tend to change the hue angle of the color dyes in a developed photographic display image. Dye hue angle is a measure in CIELAB color space of that aspect of color vision that can be related to regions of the color spectrum. For color photographic system there is a perceptual preferred dye hue angle for the yellow, magenta, and cyan dyes. It has been found that when photographic dyes are coated on support containing white pigments, the hue angle of the developed image changes compared to the hue angle of the dyes coated onto a transparent support. The hue angle change of photographic dyes caused by the presence of white pigments often reduces the quality level of the dyes compared to the dye set coated on a transparent base that is substantially free of white pigments. It would be desirable if a developed photographic dye set coated on a reflective support material had a dye hue angle that was not significantly different than the same dye set coated on a transparent support.
Prior art reflective photographic papers contain white pigments in the support just below the silver halide imaging layers to obtain image whiteness and sharpness during image exposure as the white pigment reduces the amount exposure light energy scattered by cellulose paper core. Details on the use of white pigments in highly loaded coextruded layers to obtain silver halide image sharpness and whiteness is recorded in U.S. Pat. No. 5,466,519.